All excellent things are as difficult as they are rare.

All things excellent are as difficult as they are rare.

All noble things are as difficult as they are rare

Mergers of equal partners are rare and difficult to carry out.

It is a rare and difficult attainment to grow old gracefully and happily.

and another claimed it was inherited through a parent who was a carrier of the defective gene. I had always assumed the latter was the case with Claire. After all, surely a child who grew out of grief would be born with a heavy heart.